Key Technologies for Next Generation Thin Film Silicon Solar Cells. Preparation of Ultra-Large Grain Silicon Thin-Films by Excimer-Laser.

Abstract

Advanced excimer-laser-annealing (ELA) technologies of Si thin films on glass have been reviewed. ELA-induced lateral grain growth seems attractive from an application view point since grains more than several microns in length can be grown by single shot of an excimer-laser light pulse. There are two technological ways for enhancing lateral growth kinetics. The one is introduction of non-uniform light intensity on the sample surface. Different values of thermal energy density stored in the molten Si film results in its solidification time delay along the sample surface, which triggers the long lateral grain growth. The other is an application of a non-uniform sample structure, which causes a non-uniform heat removal rate, resulting in the solidification time delay. An underlayer plays also very important role in ELA. By using organic SOG as the underlayer, grains more than 20 microns in length could be grown, and by using porous silica the grain size became more than 0.1 mm. These lateral growth technologies seem applicable not only to thin-film transistors but also to solar cells.